Ben Caradoc-Davies ha scritto:
> Andrea Aime wrote:
>> Ben Caradoc-Davies ha scritto:
>>> In 2D+1, is the main difference that the third dimension ignored by 
>>> some operations, such as coordinate transforms? I suspect 2D+1 will 
>>> be OK for line-strings, except when you try to change datum.
>>
>> Indeed. However there is no guarantee that the third dimension is
>> going to be a Z. What if it's an M? (measured shapefiles?)
> 
> Not to mention XYZM, where Z could be depth, or could be two-way-time, 
> and M is a measure (e.g. seismic sample index). Do you plan to support 
> 2D+2?

My plan is to allow support of 2D+n, no matter what the extra dimensions
are:
- they will be preserved on transformations (as you say, the meaning of
   the extra dimensions can be anything, so custom code would be needed
   to transform them anyways)
- it will be up to the code using them to decide if to use them and what
   to do with them

Mumble... we probably want some kind of descriptor of what the 
dimensions are... like, a GML encoder can encode all the dimensions
it wants but, does it make sense to encode the M in the GML?

Cheers
Andrea

-- 
Andrea Aime
OpenGeo - http://opengeo.org
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